Helcystogramma idiastis is a moth in the Gelechiidae family. It was described by Meyrick in 1916. It is known from north-eastern India. The wingspan is 10–11 mm. The forewings are grey, finely irrorated with ochreous-whitish. The stigmata is moderate, dark fuscous, laterallyedged with white, with the plical beneath the first discal. There is a terminal row of dark fuscous dots. The hindwings are light grey,. The larvae feed on Panicum species.